Proximity signaling and procedure for LTE

ABSTRACT

A method for communication in a wireless telecommunications system is provided. The method comprises receiving, by a first UE, a reference signal transmitted by a second UE and transmitting, by the first UE to a network node, a report indicating that the reference signal was received. The reference signal is received in a detection opportunity that occurs as one of a single detection opportunity or a portion of a pattern of detection opportunities.

FIELD OF THE DISCLOSURE

The present disclosure relates to the detection of the proximity ofdevices in wireless telecommunications systems.

BACKGROUND

As used herein, the term “user equipment” (alternatively “UE”) might insome cases refer to mobile devices such as mobile telephones, personaldigital assistants, handheld or laptop computers, and similar devicesthat have telecommunications capabilities. Such a UE might include adevice and its associated removable memory module, such as but notlimited to a Universal Integrated Circuit Card (UICC) that includes aSubscriber Identity Module (SIM) application, a Universal SubscriberIdentity Module (USIM) application, or a Removable User Identity Module(R-UIM) application. Alternatively, such a UE might include the deviceitself without such a module. In other cases, the term “UE” might referto devices that have similar capabilities but that are nottransportable, such as desktop computers, set-top boxes, or networkappliances. The term “UE” can also refer to any hardware or softwarecomponent that can terminate a communication session for a user. Also,the terms “user equipment,” “UE,” “user device,” and “mobile device”might be used synonymously herein.

As telecommunications technology has evolved, more advanced networkaccess equipment has been introduced that can provide services that werenot possible previously. This network access equipment might includesystems and devices that are improvements of the equivalent equipment ina traditional wireless telecommunications system. Such advanced or nextgeneration equipment may be included in evolving wireless communicationsstandards, such as long-term evolution (LTE). For example, an LTE systemmight include an Evolved Universal Terrestrial Radio Access Network(E-UTRAN) node B (eNB), a wireless access point, or a similar componentrather than a traditional base station. Any such component may bereferred to herein as an eNB, but it should be understood that such acomponent is not necessarily an eNB. Such a component may also bereferred to herein as a network node.

LTE may be said to correspond to Third Generation Partnership Project(3GPP) Release 8 (Rel-8), Release 9 (Rel-9), and Release 10 (Rel-10),and possibly also to releases beyond Release 10, while LTE Advanced(LTE-A) may be said to correspond to Release 10, Release 11 (Rel-11),and possibly also to releases beyond Release 10 and Release 11. As usedherein, the terms “legacy”, “legacy UE”, and the like might refer tosignals, UEs, and/or other entities that comply with LTE Release 10and/or earlier releases but do not comply with releases later thanRelease 10. The terms “advanced”, “advanced UE”, and the like mightrefer to signals, UEs, and/or other entities that comply with LTERelease 11 and/or later releases. While the discussion herein deals withLTE systems, the concepts are equally applicable to other wirelesssystems as well.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a diagram of a UE-UE proximity detection configured by anetwork, according to an embodiment of the disclosure.

FIG. 2 is a table of an illustrative proximity reference signal IDconfiguration, according to an embodiment of the disclosure.

FIG. 3 is a sequence diagram for a proximity reference signal, accordingto an embodiment of the disclosure.

FIG. 4 contains tables of proximity reference signal patterns, accordingto an embodiment of the disclosure.

FIG. 5 contains tables of proximity reference signal patterns, accordingto an alternative embodiment of the disclosure.

FIG. 6 is diagram of UE proximity reference signal transmissionpatterns, according to an alternative embodiment of the disclosure.

FIG. 7 is a table of an illustrative proximity reference signal IDconfiguration, according to an alternative embodiment of the disclosure.

FIG. 8 is a message flow diagram for proximity reference signalinformation acquisition, according to an embodiment of the disclosure.

FIGS. 9a and 9b illustrate a ProxRS-Config information element,according to an embodiment of the disclosure.

FIG. 10 illustrates a ProxRS-Config information element, according to analternative embodiment of the disclosure.

FIG. 11 illustrates a ProxRS-Config information element, according toanother alternative embodiment of the disclosure.

FIG. 12 illustrates a ProxRACH-ConfigDedicated information element,according to an embodiment of the disclosure.

FIG. 13 illustrates a ProxRACH-ConfigDedicated information element,according to an alternative embodiment of the disclosure.

FIG. 14 illustrates a ProxRS-DetectConfig information element, accordingto an embodiment of the disclosure.

FIG. 15 illustrates a ProxRS-DetectConfig information element, accordingto an alternative embodiment of the disclosure.

FIG. 16 illustrates a ProxRS-DetectConfig information element, accordingto another alternative embodiment of the disclosure.

FIG. 17 illustrates a ProxRSMeasurementReport message, according to anembodiment of the disclosure.

FIG. 18 illustrates a ProxRSMeasurementReport message, according to analternative embodiment of the disclosure.

FIG. 19 illustrates a ProxRSMeasurementReport message, according toanother alternative embodiment of the disclosure.

FIG. 20 illustrates a ProxRSMeasurementReport message, according to yetanother alternative embodiment of the disclosure.

FIG. 21 is a flowchart depicting a method for communication in awireless telecommunications system, according to an embodiment of thedisclosure.

FIG. 22 is a flowchart depicting a method for communication in awireless telecommunications system, according to another embodiment ofthe disclosure.

FIG. 23 is a simplified block diagram of an exemplary network elementaccording to one embodiment.

FIG. 24 is a block diagram with an example user equipment capable ofbeing used with the systems and methods in the embodiments describedherein.

FIG. 25 illustrates a processor and related components suitable forimplementing the several embodiments of the present disclosure.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents. Embodiments are describedherein in the context of an LTE wireless network or system, but can beadapted for other wireless networks or systems.

Embodiments of the present disclosure provide mechanisms and proceduresfor configuring the transmission and reception of proximity referencesignals that may be used to determine the proximity of two or more UEs.That is, an eNB may transmit to a plurality of UEs configurationinformation that specifies when the UEs are to transmit a proximityreference signal and when the UEs are to attempt to detect a proximityreference signal from another UE. A UE that has detected a proximityreference signal may inform the eNB of the detection, thereby indicatingto the eNB that the UE is in the proximity of another UE. The eNB maythen inform a plurality of UEs that they are in the proximity of oneanother. In some cases, such information may allow the UEs to engage indevice-to-device communication. The proximity reference signal may beconfigured for a single transmission and detection opportunity or formultiple transmission and detection opportunities. In the case ofmultiple transmission and detection opportunities, a set of transmissionpatterns may be configured such that each UE in a plurality of UEs hasan opportunity to detect a proximity reference signal sent by each ofthe other UEs.

LTE procedures do not currently define mechanisms to enable a UE todetermine if another UE is in direct communication range. That is, LTEdoes not specify how a UE can discover whether another UE is nearby orhow a UE can determine whether a nearby UE continues to be within range.The proximity of UEs to one another may be determined by methods notspecified by LTE, such as network-based positioning techniques, butthere is inherent error in such location measurements, particularly whenused to estimate the distance between two UEs. Further, such locationmeasurements cannot be used to determine the channel quality betweenUEs, which may be needed for further communication after proximitydetermination. In addition, since a UE has a limited battery capacity,it may not be desirable for a UE to constantly scan for signals fromother UEs.

Device-to-device communication is supported by the ad hoc mode ofunlicensed band protocols such those described in IEEE standard 802.11.In such communication techniques, a first UE may send periodic beaconsto allow a second UE to recognize the first UE and initiate adevice-to-device session. Such a scheme consumes battery power due tothe need for beaconing and scanning for other UEs' beacons. In addition,higher-layer security mechanisms may be needed to protect a UE fromunauthorized and potentially malicious communications.

In an embodiment, proximity detection between UEs may be achieved byassigning to one or more UEs a proximity reference signal (Prox-RS) thatcan be detected by other UEs. Feedback from UEs regarding detectedProx-RSs may be used by a network node, such as an eNB, to determinewhich UEs are in proximity to each other. The UEs in such a system maybe assumed to have the capability to receive and transmit controlinformation with the network node for the purpose of configuringresources for proximity discovery.

Such a system is illustrated in FIG. 1. A discoverable UE 110 may beassigned a Prox-RS with specific parameters such that nearby listeningUEs, such as UE 120, may be able to detect the Prox-RS. The listening UE120 may inform a network node 130, such as an eNB, that a Prox-RS hasbeen detected. The listening UE 120, together with the network node 130,may then determine the identity of the UE 110 transmitting the Prox-RS.

Configuration information for transmissions and receptions of theProx-RS may be sent from a network node to a plurality of UEs via radioresource control (RRC) signaling or medium access control (MAC) messagesor through other static or standardized configurations. In someembodiments, the Prox-RS may be transmitted via a signal not currentlydefined. In other embodiments, the Prox-RS may be applied to an existingsignal, such as a sounding reference signal (SRS) or any of severalphysical layer (PHY) structures including, but not limited to, physicalrandom access channels (PRACH), primary and secondary synchronizationsignals (PSS/SSS), or other reference signals or beacons.

In an embodiment, a Prox-RS may be associated with a set of parameters,such as code, cyclic shift, modulation, root sequence, and/ortime/frequency resources, that are associated with transmission of thatProx-RS. The Prox-RS parameters may also include an assignedperiodicity, which may be referred to as the Prox-RS periodicity (PRSP),for several subsequent Prox-RS transmissions. The Prox-RS parameters mayalso include a transmission pattern and its period, which may bereferred to as the proximity pattern repetition period (PPRP). Prox-RStransmissions or receptions for a UE may occur within recurringsubframes, which may be referred to as Prox-RS opportunities. That is, aProx-RS opportunity may be defined as a set of periodically recurringtime/frequency resources in which a UE may be configured to transmit aProx-RS, and the Prox-RS opportunities may recur with the PPRP. TheProx-RS parameters may define specific resources for a plurality ofProx-RS transmissions, wherein the set of Prox-RSs for a plurality ofUEs is configured such that each UE has an opportunity to transmit toand listen to each of the other UEs. A discoverable UE that is alsolistening may be configured to detect other UEs' Prox-RS transmissionsin Prox-RS opportunities when it is configured to not transmit. TheProx-RS parameters may further specify that Prox-RS transmissionsdiscontinue after a specific number of transmissions or a specifiedlength of time.

The Prox-RS opportunities may be single subframes or orthogonalfrequency division multiplexing (OFDM) symbols or a set oftime/frequency resources that may recur periodically. In an embodiment,a Prox-RS may be configured to occur in a specific OFDM symbol of asubframe, such as every n^(th) subframe where n is an integer one orgreater. In another embodiment, Prox-RS opportunities may be a set ofperiodically recurring adjacent or substantially adjacent symbols orsubframes in which a UE may be configured to transmit a Prox-RS.Constraining a set of Prox-RS opportunities to occupy a small number ofadjacent subframes may improve UE battery life by allowing the UE to‘sleep’ longer between subframes in which it receives or transmits aProx-RS. By contrast, if a UE must ‘wake up’ to transmit or receiveProx-RS in non-adjacent subframes, there will be more transition periodsto and from its sleeping state, leading to extra use of battery powerduring the transitions. In summary, an assigned Prox-RS may consist of asingle Prox-RS transmission, a series of repeated Prox-RS transmissions,a series of periodic Prox-RS transmissions, and/or a series of Prox-RStransmissions with an assigned pattern.

In an embodiment, a UE may be assigned a Prox-RS via the configurationof a Prox-RS identifier that may uniquely identify a Prox-RS and thatmay be referred to as the Prox-RS ID. If a UE is assigned a Prox-RS ID,the Prox-RS ID may provide a pattern indicating the Prox-RS opportunityresources in which a UE is to transmit its assigned Prox-RS and theopportunities in which the UE should not transmit its Prox-RS. TheProx-RS ID may be associated with a set of parameters for transmissionof that Prox-RS, such as time/frequency resources and/or otherparameters mentioned above. For example, if the Prox-RS uses the SRS,the Prox-RS ID may define the root sequence, the cyclic shift, theperiodicity, and other transmission parameters of the SRS assignment.The parameters associated with the Prox-RS ID may be standardized andmade known to a plurality of UEs and an eNB. In this way, a UE may beconfigured to transmit or detect a Prox-RS with a specific set ofparameters by an indication of the Prox-RS ID, rather than an explicitlisting of the parameters. However, the common resources for all Prox-RStransmissions in a cell may still need to be indicated to the UE.

In an embodiment, the Prox-RS assignment to a UE provides distinctreception patterns as well as transmission patterns. The transmissionpatterns indicate in which Prox-RS opportunity resources a UE is totransmit its assigned Prox-RS, whereas the reception patterns indicatein which Prox-RS opportunity resources a UE is to attempt to detectProx-RS transmissions. A discoverable UE that is also listening may beconfigured to detect Prox-RS transmissions in Prox-RS resourcesaccording to a reception pattern. If the transmission and receptionpatterns “collide” such that a UE would simultaneously receive andtransmit on a resource, a rule may be used to resolve the collision. Forexample, the rule may be that the UE only transmits when there is acollision or that the UE only receives when there is a collision.

Prox-RS transmission opportunities may be periodic, but for a singleProx-RS pattern, transmissions may not occur periodically. For a givenProx-RS pattern, the pattern may be repeated with the PPRP that isreceived as part of Prox-RS configuration, but the pattern itself maynot contain periodic Prox-RS transmissions. For example, if a UE isassigned the Prox-RS ID 1 pattern in Table 1 in FIG. 2, the UE willtransmit in the Prox-RS opportunity in the first frame and second frame,but not in the third frame or fourth frame. The UE will then beginrepeating the pattern by transmitting in again in the fifth and sixthframe opportunities, but not the seventh and eighth frames. Hence, itcan be seen the UE does not transmit periodically as it does nottransmit in each frame, but the UE does transmit according to a patternthat is periodic and does repeat.

For example, if a Prox-RS is one sequence from a set of cyclicallyshifted Zadoff-Chu sequences based on a common root, the Prox-RS ID maybe configured such that, for each Prox-RS ID, there is a correspondingcyclic shift and transmission pattern, as shown in Table 1. In addition,the signal configuration in Table 1 may comprise parameters such asresources or a frequency hopping pattern, or a base sequence/codegenerator may be added to the table.

A discoverable UE assigned a Prox-RS ID may transmit the assigned signalaccording to such a pattern on periodically allocated Prox-RS resources.Upon completion of the pattern, the UE may repeat the pattern untilde-assignment of that proximity configuration or until the end of theconfigured transmission window. For example, in FIG. 3, UE1 istransmitting based on the periodically occurring resources according toID 1 from Table 1. In the first four opportunities, UE1 follows theassigned pattern of transmitting twice and then muting twice. The UEbegins the pattern again in the fifth opportunity. During theopportunities where the UE is muted from transmitting its Prox-RS, itmay be configured to listen for Prox-RSs from other UEs.

While Table 1 shows a fixed finite table of aligned patterns, additionalUEs that need proximity indication may be added to a system at any time.For example, when a first UE that desires proximity indication entersthe system, the eNB may assign pattern ID 1 to the UE. When the next UEenters the system, the eNB may assign pattern ID 2, and so on.Additional UEs that request proximity service may be provided one of theavailable patterns or Prox-RS IDs from the set of defined patterns orProx-RS IDs. If there are more UEs than the number of currentlyconfigured patterns, the eNB may assign a new resource set (time,frequency, code, etc.) and allocate Prox-RS IDs or patterns in that newset of resources to the additional UEs.

Alternatively, patterns may be generated according to pseudo-randomsequences that are known or can be derived at the transmitting UE andreceiving UE. For example, a UE may use or be assigned a pseudo-randomsequence, where each element of the sequence corresponds to eithertransmission (e.g., “1”) or muting (e.g., “0”). Different UEs may beassigned different sequences. Alternatively, sequences may be derived atleast in part from the UE ID (such as the cell radio network temporaryidentifier (C-RNTI)) or some other seed.

In an embodiment, the patterns may be constructed so that within eachset of patterns each UE in a plurality of UEs is ensured to have atleast one opportunity to receive a Prox-RS from each of the other UEsduring one cycle of the pattern. For a small number of UEs, a simplepattern set such as one UE transmitting in each opportunity may be used.For a larger number of UEs, a pattern that minimizes the total time fora set of transmissions may be used, where the total time is related tothe number of time division opportunities.

More specifically, for a larger numbers of UEs, a binary tree may beemployed, resulting in T=2┌log₂ N┐ time resources, where N is the numberof discoverable UEs. For example, in the simplified case in whichN=2^(n), an N-way discovery problem exists. The UEs may be divided intotwo groups, A₁ and A₂, each with N/2 UEs. In the first time unit, UEs inA₁ may transmit Prox-RS and UEs in A₂ may receive Prox-RS. UEs in A₂ maypreferably monitor all Prox-RSs in A₁. In the second time unit, UEs inA₂ may transmit and UEs in A₁ may receive. So, after two time units,each UE in A₁ has received once from each UE in A₂ and vice versa. Asubsequent step may ensure that all UEs in A₁ receive from each other atleast once and that all UEs in A₂ also receive from each other at leastonce. Two N/2-way discovery problems now exist. These two discoveryproblems may be solved simultaneously by repeating the first step foreach of A₁ and A₂. That is, A₁ may be divided into A₁₁ and A₁₂, and twotime units may be spent for the UEs in A₁₁ and A₁₂ to discover eachother. These steps may continue until there is only one UE in each set.The number of such steps is n or log₂(N). Since two time units areneeded in each step, the total number of required time units is2*log₂(N). If N is not an integer exponent of 2, then the requirednumber of time units is 2┌log₂ N┐. If at least N/2 Prox-RS resources areavailable for each of the time instances, the amount of resources usedover the time instances is equal to N/2×2┌log₂ N┐=N log₂(N).

The Prox-RS patterns may be expanded to the cases for eight or 16Prox-RS IDs, cyclic shifts, and patterns. An embodiment of a Prox-RSpattern for eight Prox-RS IDs is illustrated in Table 2 in FIG. 4, andan embodiment of a Prox-RS pattern for 16 Prox-RS IDs is illustrated inTable 3 in FIG. 4.

Tables 1, 2, and 3 illustrate binary tree-type patterns. In anotherconfiguration, each transmitter transmits its Prox-RS sequentially, withall other receivers listening. Embodiments of Prox-RS patterns for eightand 16 Prox-RS IDs with sequential transmission are illustrated inTables 4 and 5, respectively, in FIG. 5. For eight Prox-RS IDs, eighttime resources are needed (as opposed to six in Table 2), and for 16Prox-RS IDs, 16 time resources are needed (as opposed to eight in Table3). The sequential table formats in Tables 4 and 5 have the advantage ofhaving a UE transmit only once per Prox-RS ID pattern period, therebysaving battery power associated with transmission.

In an embodiment, patterns may be constructed to minimize the totalProx-RS resources used in a discovery cycle. For example, p UEs may senda Prox-RS in one time unit and N-p UEs may receive these transmissions.Multiplexing p UEs at a time, N/p=q units of time may be required toallow each UE to send one Prox-RS transmission. However, the UEs thatare multiplexed in the same time unit may not receive each other'sProx-RS transmissions. In order for the UEs to receive each other'sProx-RS transmissions, each UE may have to transmit one more time, thistime multiplexed with UEs that were not multiplexed together duringtheir first transmission. This can be accomplished in another p timeunits. Thus, in a total of p+q time units, all of the p×q=N UEs may sendand receive Prox-RS transmissions from each other. Minimizing for (p+q)results in p=q=√N. Hence, a Prox-RS transmission pattern that minimizesthe total Prox-RS resources for a given set of N UEs may be one thatmultiplexes √N Prox-RS resources per time unit and has a pattern of √Ntime units or Prox-RS opportunities.

In an embodiment, a set of Prox-RS patterns may be configured orotherwise made known to the UEs in addition to the particular instanceof the pattern that a UE is expected to follow. In an embodiment, theeNB may compute patterns specific to each UE and convey a pattern to aUE. For example, a pattern transmit and receive of length 16 may beconveyed by a length-16 field of a Prox-RS configuration message, suchas an RRC message. The Prox-RS configuration may be provided or changedafter a UE sends an indication for proximity interest.

A receiving UE may use the knowledge of a discoverable UE's Prox-RSpattern to listen for the discoverable UE's Prox-RS in multipleopportunities. The receiving UE may soft combine the received signalsprior to a decision regarding the presence or absence of thediscoverable UE's proximity signal. Thus, knowing the pattern may aidthe receiving UE in knowing which Prox-RS opportunities to use when softcombining the Prox-RSs.

In an embodiment, if the Prox-RS pattern is not known to listening UEs,the listening UEs may report per RS period. These reports may beconsolidated by the network node, which may know the RSs that weretransmitted. The network node may then determine the proximities of theUEs based on the consolidated reports.

In an embodiment, the listening UEs may be aware of the Prox-RSperiodicity and the pattern periodicity without knowing the exacttransmission pattern of the discoverable UEs. A listening UE may thendetermine the pattern as well as the proximity.

In an embodiment, the Prox-RS ID may refer to a unique signal for a UEto use in specific Prox-RS resources. This unique signal may differ fromanother signal in cyclic shifts, base sequences, code generators, and/orother signal parameters. For example, FIG. 6 illustrates UE Prox-RStransmission patterns according to the Prox-RS ID assignments inTable 1. A UE may be assigned a unique signal within the resources shownsuch that UEs that expect to receive in a particular Prox-RS resourceare able to distinguish the transmitting UEs uniquely from othertransmitting UEs in the same Prox-RS resources. Therefore, detection ofa Prox-RS in any Prox-RS transmission opportunity is sufficient touniquely identify a nearby UE.

In an embodiment, a Prox-RS ID may refer to a unique signal for a UE touse in specific Prox-RS transmission opportunities, but that signal maybe defined by a second Prox-RS ID for use by a second UE during Prox-RStransmission opportunities in which the first UE is muted. This isexemplified in the patterns given in Table 6 in FIG. 7. In this example,the first set of four UEs use the transmission patterns according toTable 1 and as illustrated in FIG. 6. The second complementary set ofUEs—UE5, UE6, UE7, and UE8—reuse the same signals but in oppositepatterns to the first set. For example, UE5, using the opposite patternto UE1, transmits a signal with cyclic shift 1 in the pattern RRTT.Within each set, each UE is ensured to have at least one opportunity toreceive from all other UEs in the set and also have its transmissionreceived by all others in the set. However, this is not ensured betweenUEs of different sets. Therefore, to identify a nearby UE, a receivingUE may need to report both the received signal and the correspondingtransmission opportunity to the network node. In Table 6, if all IDs arein use, then each UE may detect only six of the seven other UEs usingthis scheme.

Such a method may be used in embodiments where it is not essential forone set, such as IDs 1-4, to detect another set, such as IDs 5-8. Such aconfiguration may be used when resources are used for differentproximity services or procedures or for different discovery groups.Multiplexing the sets of Prox-RS patterns in this manner may allow oneset of resources to be used for both sets of patterns and hence mayreduce the overall number of resources needed for the two sets.

The network may assign a UE a Prox-RS ID for use in specific resourcesfor a single transmission or for limited-time transmissions. In the caseof a single transmission, the UE may transmit the Prox-RS signalaccording to the parameters of the Prox-RS ID once. In the case oflimited-time transmissions, the UE may transmit the Prox-RS signalaccording to the parameters of the Prox-RS ID one or more times asdirected by the configuration parameters. The Prox-RS transmissions mayterminate in the latter case without the need of an additional RRCmessage to reconfigure the assignment.

In an embodiment, limited-time transmissions may be configured as singletransmissions. For example, a UE may be configured for a singletransmission of a random access channel (RACH) preamble by the eNB.Alternatively, limited-time transmissions may be configured as repeatedtransmissions. For example, a UE may be configured with a RACH preambleand mask (as per RACH configuration in LTE) for multiple transmissions.In some embodiments, the single transmission is indicated by a physicaldownlink control channel (PDCCH) signal. The PDCCH signal may be in theform of a Device Control Information (DCI) that contains a set of fieldsthat when interpreted together by a device configured to perform limitedtime proximity (e.g., via RRC messages) indicate that proximity signalcommand from the eNB. The command may be for a proximity signaltransmission or reception to be performed by the device. In someembodiments, the DCI may contain indications for several devices toperform proximity transmission or reception.

The Prox-RS may be used in conjunction with the discontinuous reception(DRX) states in a UE. In an embodiment, a Prox-RS configuration includesan indication of the UE action in cases where Prox-RS transmission isconfigured to occur when the UE is in DRX OFF state and in cases whereProx-RS transmission is configured to occur when the UE is in DRX ONstate.

In an embodiment, when the UE is in DRX OFF state, in the subset ofsubframes where the Prox-RS is configured to be transmitted and/orreceived by a UE, the UE transmits or receives the Prox-RS, but need notreceive the PDCCH and therefore may not receive the physical downlinkshared channel (PDSCH) or transmit on the physical uplink shared channel(PUSCH). As such, the UE's function is the same as in the typical DRXOFF state, with an exception made for the transmission or reception ofthe Prox-RS. Further, the measurement report of the received Prox-RS mayoccur only when the UE is in DRX ON state. In an embodiment, a UEremains in DRX OFF state for only the transmission or the reception ofthe Prox-RS signals, but not both.

In an embodiment, in the subset of subframes where the Prox-RS isconfigured to be transmitted or received, the UE is in DRX ON state. Ifthe UE was otherwise in DRX OFF state, the UE transitions to DRX ONstate for the subframes where the UE is configured to transmit orreceive Prox-RS. In an embodiment, the configuration provided to a UEindicates that the UE shall remain in DRX ON state for only thetransmission or the reception of the Prox-RS signals, but not both.

In an embodiment, the configuration may indicate that transmission ofthe Prox-RS signals is to be suspended if the UE is in DRX OFF state. Inan embodiment, the configuration may indicate that reception of theProx-RS signals is to be suspended if the UE is in DRX OFF state.

In some embodiments, the configuration of a UE's actions in DRX isspecified in an eNB configuration or a standards specification insteadof being transmitted to the UE along with transmission or detectionconfigurations.

In an embodiment, a UE may be configured to attempt detection of aProx-RS from other UEs in either a “promiscuous” mode or a “directed”mode. In the promiscuous mode, the UE listens for all of the Prox-RSsand reports those that were detected to the network node. In thedirected mode, the UE is configured by the network node to listen for asubset of the Prox-RSs and report only those within the subset that weredetected. The subset may refer to a subset of resources, timeopportunities, and/or specific patterns or signals.

In either mode, reporting of the detected signals may entail eitherbinary decision detection or further detailed signal strengthmeasurements of one or more received Prox-RS signals. That is, signalstrength may be quantized by a one-bit response that indicates receptionof the Prox-RS above a threshold or by a multiple-bit signal strengthmeasurement that can provide further detail of the Prox-RS power, suchas a quantized dBm measurement.

In the promiscuous detection mode, a UE attempts detection of allpossible Prox-RSs for a cell, network node, or network. For example, aUE connected to a cell may attempt to receive all Prox-RSs that the UEis aware of, such as the Prox-RSs that are configured for that cell. TheUE may obtain information regarding the configured Prox-RSs from asystem information broadcast (SIB) or RRC messaging. For example, a UEmay be aware of the possible preambles (e.g., RACH configurations) orcyclic shifts (e.g., SRS type configurations) for a given common Prox-RSresource configuration from a standards specification or otherwise. TheUE may then be signaled one or more Prox-RS common configurations viaRRC or SIB and begin detection of possible Prox-RS transmissions inthose resources. For example, if a Prox-RS is configured as an SRStransmission, then the UE may be signaled the Prox-RS as an SRS commonconfiguration. The Prox-RS configurations allowed may be a subset ofthose for SRS and may be only periodically occurring Prox-RS with one of16 cyclic shifts. A UE employing promiscuous detection may then searchthe Prox-RS resources for those cyclic shifts according to standardizedand signaled configurations.

In an embodiment, a UE may be instructed by the network node to listenfor all Prox-RSs from one or more neighboring cells. Alternatively, theUE may be configured to attempt to detect all Prox-RSs for any cell thatmay be in the network. Such a configuration may be given by the networknode or may be a static or standardized configuration.

In an embodiment, a UE may be informed of the set of Prox-RSs to monitorpartially from signaling, such as RRC or SIB, and partially fromstandardization or configuration. In this way, the signaling to indicatethe set of Prox-RSs to monitor may be reduced. For example, if SRS isused for Prox-RS signaling, the eNB may indicate an SRS configurationconsisting of one or more resource locations and/or base sequences inuse. The UE may already know how an SRS is signaled from standardizationor configurations, as well as possible cyclic shifts in use for Prox-RSpurposes and possible transmission patterns. One or more otherparameters may be standardized or known from a configuration andtherefore may not have to be explicitly signaled, such as the SRSbandwidth or the set of base sequences.

In some cases of promiscuous detection, the UE may not be provided withan indication of which Prox-RSs are in use at given time but may belimited to information regarding the possible set of Prox-RSs that maybe in use or could potentially be configured. Whether or not a Prox-RSin use is signaled may depend on signaling overhead limitations and theease of representing whether or not the Prox-RS is in use given the setof configurations. The manner in which a UE detects and reports theseProx-RSs may depend on whether a known pattern or a single transmissionof Prox-RS has been defined. Both may be defined, so a combination ofreporting may be configured.

In an embodiment, a UE that has detected a Prox-RS may report thedetected Prox-RS to a network node, for example, by reporting thesubframe, resource, code sequence, or other parameters of the detectedProx-RS. Detections may be reported on the physical uplink controlchannel (PUCCH), MAC, or RRC channels, but RRC may be the most usefulmessaging. The UE may report the set of Prox-RS IDs detected.Alternatively, the UE may report a positive acknowledgement (ACK) ornegative acknowledgement (NACK) of whether or not a particular Prox-RSID was detected. The detection of a Prox-RS ID may be reported as abitmap, with each element of the bitmap corresponding to a Prox-RS IDand the value of each element of the bitmap corresponding to thepresence or absence of that Prox-RS ID. For example, a UE may beconfigured to detect all Prox-RSs associated with a set of resourcesdefined by the eNB. Given the Prox-RS resource configuration, the UE maydetermine from standards specification and configuration parameters thatthe number of possible Prox-RSs is N. The UE may then report a bitmapindicating the detection of any of the configured possible Prox-RSs.

In other cases, the UE attempts to detect a Prox-RS according to asingle transmission of a Prox-RS signal in a specific Prox-RS resourceor set of resources. While a detection report may be based on a singledetection or attempted detection, the Prox-RS signal transmitted mayhave been configured as a pattern of transmissions or a singletransmission from a UE. In some embodiments, the UE may report to theeNB individual parameters of the detected Prox-RS, such as the basesequence, cyclic shift, time and/or frequency resource. In otherembodiments, the UE may report the Prox-RS ID corresponding to theparameters of the detected signal. The detections may be reportedthrough RRC or MAC signaling.

In other embodiments, the UE may simply report an ACK or NACK to the eNBcorresponding to the detected presence or absence of a signal with theparameters specified by the network node. In such a reporting scheme, aUE in the promiscuous mode may attempt to detect all signals in a singletransmission opportunity and may report whether or not each of thepotential signals is detected. In some cases, each opportunity is asingle resource for one Prox-RS ID, and hence for each opportunity onlyone report (“ACK/NACK”) may be required. In other cases, an opportunitymay consist of potentially many signals being detected, and hence thereport may need to have multiple indications.

In some cases, the Prox-RS pattern may not be known to detecting UEs,and the UEs may report per RS period to the eNB. In an embodiment, thesereports may be consolidated by the network node if the network nodeknows which Prox-RSs were transmitted. The consolidated reports may thenbe used to derive proximity. If there is a mix of single transmissionsand known transmission patterns present in a resource, the UE may beconfigured to report according to the single transmission method. The UEmay report immediately after detecting a Prox-RS transmission, or the UEmay be configured to store Prox-RS detections over a reporting period orinterval.

As mentioned above, in addition to the promiscuous mode just described,detection of a Prox-RS may occur in a network-directed mode. In thedirected mode, a UE is configured by a network node to listen for asubset of the Prox-RS. The subset may refer to a subset of resources,time opportunities, and/or specific patterns or signals. The subset maybe defined by a list of Prox-RS IDs or by a set of Prox-RS configurationparameters, such as base sequence, cyclic shift, and time and/orfrequency resources. The UE may be configured to listen for a subset ofProx-RSs by RRC signaling. The network node may update this informationas the Prox-RSs in use change. Detecting a subset of the Prox-RSs maysignificantly reduce the complexity of detection at the UE.

In an embodiment, the UE may report the set of Prox-RS IDs detected.Alternatively, the UE may report an ACK or NACK to indicate whether ornot a particular Prox-RS ID was detected. The ACK or NACK may bereported as a bitmap, with each element of the bitmap corresponding to aProx-RS ID and the value of each element of the bitmap corresponding tothe detection or absence of detection of that Prox-RS ID. Alternatively,the UE may report individual parameters of the detected Prox-RS, such asbase sequence, cyclic shift, and time/frequency resources. The UE mayreport immediately after detecting a configured Prox-RS transmission ormay be configured to store Prox-RS detections over a reporting period orinterval.

In an embodiment of the directed mode, the UE may attempt to detectProx-RS according to the known transmission patterns, sequences, andProx-RS locations defined for each Prox-RS ID that the UE is configuredto detect. As described above, if a pattern is defined for a Prox-RS ID,the UE may utilize soft combining of multiple transmissions in order toenhance the Prox-RS signal reception. In another embodiment of thedirected mode, the UE may attempt to detect Prox-RS according to asingle transmission of each Prox-RS ID for which the UE is configured tolisten. In either case, the UE may use the information regarding theparameters for each Prox-RS ID to determine which of the Prox-RSs arepresent.

The UE may report the set of Prox-RS IDs detected from the set the UEwas configured to listen for. Alternatively, the UE may report an ACK orNACK regarding whether or not a particular Prox-RS ID was detected. Ineither case, the report may be transmitted by one of multiple channels,including a MAC message or an RRC message. In some cases, the UE mayreport parameters of the detected Prox-RS according to the directeddetection configuration. For example, the UE may report information thatindicates the sequence detected, the Prox-RS resource index, and/or thetime location of the Prox-RS resources.

This detection and reporting procedure may be used when one or more UEsare configured for single transmission of a Prox-RS. Alternatively, a UEmay attempt to detect single instances of Prox-RS transmissions from UEsassigned a Prox-RS transmission pattern. However, this pattern may ormay not be known to the detecting UE.

The detection reports may be consolidated by the network node if thenetwork node knows which Prox-RSs were transmitted. The consolidatedreports may then be used to derive proximity. For example, a UE mayreport the detected proximity signals via RRC. The UE may report theparameters of the Prox-RSs detected in a given proximity opportunityalong with the proximity opportunity identifier, such as the subframe orframe number of the proximity opportunity. If the UE is directed todetect a specific set of single transmissions, the eNB may assignvirtual Prox-RS IDs to each of these directed detections, in which casethe UE may need to report only the virtual Prox-RS IDs detected ratherthan detailed parameters. The UE may further combine several reportsfrom several proximity opportunity detections into an RRC message. Themay UE report immediately after detecting a Prox-RS transmission or maybe configured to store Prox-RS detections over a reporting period orinterval.

In an embodiment, a network node may provide further detectionassistance information to improve Prox-RS detection at the UE. Forexample, the network node may provide a UE with the set of Prox-RSs inuse. Using this information, the UE may more reliably detect theProx-RSs in use as the UE can eliminate the possibility of transmissionof Prox-RSs that are not currently assigned. Such assistance informationmay be used in the promiscuous mode, where the UE is searching for allProx-RSs, and also in the network node-directed mode, where the UE issearching for a subset of the configured Prox-RSs. In the promiscuousmode, the UE may use this additional information to limit its search anddetection to the set of Prox-RSs in use rather than all thosepotentially configured. In the network node-directed mode, the UE mayuse this information not to limit its search, but to aid in its networknode directed Prox-RS searches by knowing that the remaining configuredProx-RSs in use are potential sources of false detections.

As an example of the latter case, a scenario may be considered where anSRS-like signal is used as a Prox-RS and only cyclic shifts (CS) 1, 3,5, and 7 are configured to be used. UE1 may be assigned CS1 as itsProx-RS, and UE2 may be directed to detect the proximity of UE1 byattempting to detect the existence of CS1. If the receiving UE2 is notaware that only CS 1, 3, 5, and 7 are used, there is a chance that CS2may be erroneously detected (i.e., a false detection), and UE1 (withProx-RS CS1) may be declared not to be in the proximity (i.e., a misseddetection). In this case, to improve detection, the network node mayprovide UE2 with the set of Prox-RSs in use (i.e., CS 1, 3, 5, and 7).UE2 may then be able to eliminate CS2 as a potential Prox-RS andpotentially increase its possibility of correctly detecting CS 1.

In an embodiment, when Prox-RS transmissions are ongoing and follow aknown pattern, a first listening UE may be configured to track a secondtransmitting UE in order to obtain proximity information from the secondUE at a future time. The first UE may be configured to detect theproximity of the second UE according to one of the methods describedabove. After the second UE is detected, the first UE may continue tolisten for the Prox-RS of the second UE in order to track the proximityof the second UE. In an embodiment, when a UE is first directed by anetwork node to detect the proximity of another UE, the indication todetect proximity may also imply tracking the other UE.

For example, an eNB may note that among a plurality of UEs there is aUE2 that is of particular interest to UE1. In this case, the eNB mayconfigure UE1 with a Prox-RS configuration that does not require the UE1to detect proximity with UEs other than UE2 or may configure UE1 todetect proximity with the other UEs less frequently. In such a case, UE1may be said to be tracking UE2. Further, it may happen that UE2 isinterested in proximity information with UE1 more than with other UEs.In such cases, a similar configuration may be provided to UE2.

In an embodiment, when a UE is tracking another UE, the tracking UE maynot report the Prox-RS detection of the other UE to the network nodeafter the initial detection. In other embodiments, the reporting ofProx-RS after initial detection may be less frequent than initialdetection reporting. In some embodiments, after the initial detectionand reporting of the detection, the tracking UE may not report thedetected Prox-RS again until the expiration of a timer that was reset atthe time of the last report or detection or until configured orrequested to do so by the network node. In other embodiments, after theinitial detection and reporting of the detection, the tracking UE mayreport to the network node only when the tracking UE determines that theother UE is out of proximity.

In some cases, a UE or the eNB may determine the need to discontinueProx-RS assignments. For example, a UE may no longer need to allow otherUEs to determine its proximity, or a UE may decide to discontinueproximity detection functions to save battery life and therefore mayterminate its allocation of Prox-RS. Alternatively, the eNB may decideto discontinue the allocation of the Prox-RS to a UE. The termination ofProx-RS transmissions and/or detections for a given UE may be achievedthrough additional RRC signaling to the UE or a MAC reconfigurationmessage to the UE. Alternatively, rather than waiting for an explicitRRC or MAC reconfiguration, a UE may be assigned Prox-RSs with a patternassignment that expires. The expiration may be controlled by a timerthat runs for a specified period of time after being activated upon theinitial configuration of the Prox-RS or the first transmission of theProx-RS. Alternatively, the expiration may be a maximum number oftransmissions that is activated upon the first transmission of theProx-RS. For example, the number of transmission may be equal to “1′” inthe case of single transmission Prox-RS configurations. In eitheralternative, the expiration value may be specified in the standardspecifications or configured in a RRC reconfiguration message.

Details will now be provided regarding the messages that may be used fortransmission configuration, detection configuration, and reporting. Thediscussion hereinafter will focus on RRC messages, but similarconsiderations may apply to MAC messages.

The configuration of a Prox-RS pattern may be given in an RRC messagesuch as that illustrated in FIG. 8, where a network node 810, such as aneNB, sends a Prox-RS configuration message 820 to a UE 830. A similardiagram may apply to the transmission of a detection configurationmessage. In the case of a reporting message, the message would be sentfrom the UE 830 to the network node 810.

As mentioned above, the Prox-RS may use SRS signaling, and hence theconfiguration message for a transmission pattern may be based on theSRS-Config information element (IE). Two IEs are disclosed herein: acommon configuration for assigned resources for all Prox-RSs and adedicated configuration of the Prox-RS for use by a UE.

In an embodiment, a new set of resources may be used for the Prox-RStransmissions, in which case a ProxRS-ConfigCommon IE may be included inan RRC message to UEs. Alternatively, where the Prox-RS reuses resourcesfor SRS transmissions, the ProxRS-ConfigCommon IE may not be sent.However, an SRS-ConfigCommon IE may be included. In an embodiment, aProxRS-Config IE (with common and dedicated parts) may be defined asshown in FIGS. 9a and 9b . In FIGS. 9a, 9b , and subsequent figures,newly disclosed items are underlined and deleted items are strickenthrough.

In an alternative ProxRS-Config IE, the proxrs-ConfigIndex parameter andcyclicshift parameter may be included in a single table, as in Table 1of FIG. 2, where a configuration and a cyclic shift are given by theProx-RS ID. Such an alternative ProxRS-Config is shown in FIG. 10.

In an embodiment, the parameters proxrs-Bandwidth,proxrs-HoppingBandwidth, freqDomainPosition, and transmissionComb may beindicated by the Prox-RS ID and hence may not need to be included in anIE. An example of such an alternative IE is illustrated in FIG. 11.

In an embodiment, the Prox-RS may reuse RACH-type signaling. In suchcases, a variant of the RACH-ConfigDedicated IE may be used to assignthe Prox-RS to a UE. This IE may be denoted as ProxRACH-ConfigDedicatedwhen the physical RACH signal is used as the Prox-RS. The time/frequencyresources used for Prox-RS using RACH may be the same as those for theRACH, or additional time/frequency resources may be assigned for Prox-RSusing RACH. An example ProxRACH-ConfigDedicated IE is illustrated inFIG. 12.

In an embodiment, when a UE is be assigned to transmit the Prox-RS as arecurring Prox-RACH, a duration field may be used to indicate whether asingle transmission, multiple transmissions, or indefinite transmissionof the dedicated Prox-RS is assigned. An example of such an alternativeProxRACH-ConfigDedicated IE is illustrated in FIG. 13.

As in the case of Prox-RS transmission configuration, a message for aProx-RS detection configuration may be based on the SRS-Config IE. Twotypes of IEs are disclosed herein: a common configuration for assignedresources for all Prox-RSs and a dedicated detection configuration ofthe Prox-RS for use by the UE.

In an embodiment, a new set of resources may be used for the Prox-RStransmissions, in which case a ProxRS-ConfigCommon may be included in anRRC message to UEs for detection. Alternatively, where the Prox-RSreuses resources for SRS transmissions, the ProxRS-ConfigCommon may notbe sent. However, an SRS-ConfigCommon may be included.

In some embodiments, the eNB may send the same Prox-RS configuration tomore than one UE. For example, the eNB may send a configuration forProx-RS ID #1 and associated parameters in an RRC message and then sendanother configuration for Prox-RS ID #1 and associated parameters to asecond UE in a separate RRC message such that both UEs may transmit thesame Prox-RS on the same resources. This common Prox-RS assignment maysimplify detection in cases of a large number of UEs.

In some embodiments, as part of a multiple step proximity detectionmethod, a UE may receive at least one additional Prox-RS configurationafter receiving an initial Prox-RS configuration. The additional Prox-RSconfiguration may be sent to the UE by an eNB after the eNB has receiveda detection report pertaining to the UE. In such a multi-step method, afirst UE may transmit a Prox-RS that is commonly assigned to at leastone other UE. Once detected by a second UE and reported to the eNB,further disambiguation of the UE may be needed if UE-specific proximityis desired. In such cases, the first UE may be assigned another Prox-RSfor the second UE to detect in a second stage of the proximity detectionprocedure. Two or more stages may be needed depending on the number ofProx-RS available, among other factors.

Two types of detection configuration IEs are disclosed herein: aneNB-directed detection configuration IE and a promiscuous detectionconfiguration IE, corresponding to the two detection modes disclosedabove. For the eNB-directed detection configuration, an exampleProxRS-DetectConfig IE (with common and dedicated parts) is illustratedin FIG. 14. For the promiscuous detection configuration, an exampleProxRS-DetectConfig IE (with common and dedicated parts) is illustratedin FIG. 15.

In some embodiments, the UE determines the resources for promiscuousdetection from a broadcast system information block (SIB) rather than anRRC. In these cases, a UE may receive the Prox-RS-ConfigCommon asillustrated in FIG. 15 in an SIB rather than RRC message. The UE may notreceive an RRC message for reporting configuration in this case and mayuse a defined measurement report IE for this purpose. Note that a UE maybe in RRC IDLE or RRC connected mode when receiving the SIB. If the UEwas in RRC IDLE mode when performing promiscuous detection of Prox-RSsignals, the UE may initiate RRC connection establishment prior toreporting to the eNB.

In an embodiment, the transmission configuration message may be combinedwith the detection configuration message. For example, in the case oftransmission of a Prox-RS and detection of all other Prox-RSs on theProx-RS common resources, the ProxRS-Config IE in FIG. 16 may betransmitted.

In an embodiment, a detected Prox-RS may be reported in a newmeasurement report, or a report of the detection may be added to themeasurementreport defined in 3GPP Technical Specification (TS) 36.331.In some measurement reports, the UE may specify the signal strength ofthe Prox-RS based on the Prox-RS virtual id (proxrs-vid) indicated inthe detection configuration RRC message. For example, a newProxRSMeasurementReport message may be defined as illustrated in FIG.17.

In other measurement reports, the UE may specify the signal strength ofthe Prox-RS based on the Prox-RS ID (proxrs-ld) as specified in astandard or otherwise configured. An example of such a message isillustrated in FIG. 18.

In still other measurement reports, the UE may specify the signalstrength of the Prox-RS based on the Prox-RS ID parameters as measured.For example, for the SRS-type Prox-RS, the cyclic shift andconfiguration index may be the primary means for identification, asillustrated in FIG. 19.

In another example, for the RACH-type Prox-RS, the preamble index andPRACH subframe may be the primary means for identification, asillustrated in FIG. 20.

The preceding discussion has been directed toward the configuration,detection, and reporting of proximity signals within the coverage of anetwork. The embodiments described may be applicable in the absence ofnetwork coverage if a UE receives relevant information from sourcesother than from the network directly. For example, the UE may be given aProx-RS transmission, detection, and/or reporting configuration via asemi-static configuration, potentially from downloadable sources or someother pre-provisioning of the configuration. In the case of Prox-RStransmission, the configuration may alternatively be determined by therandom selection of a proximity signal from a configured set of signals.In addition, timing synchronization may be required in order for UEs todiscover other UEs and for patterns to be reused as described above. Inthe absence of the network, such time synchronization may be provided byone or more of the UEs.

An embodiment of a method for communication in a wirelesstelecommunications system is illustrated in FIG. 21. At block 2110, a UEreceives configuration information specifying at least one transmissionopportunity in which the UE is to transmit a first reference signal andfurther specifying at least one parameter applicable to the transmissionof the first reference signal. At block 2120, the UE transmits the firstreference signal in the specified transmission opportunity. At block2130, the UE attempts to detect a second reference signal that has atleast one parameter that is the same as a parameter of the firstreference signal. The detection attempt occurs in a detectionopportunity that occurs at a different time from the transmissionopportunity.

An embodiment of another method for communication in a wirelesstelecommunications system is illustrated in FIG. 22. At block 2210, afirst UE receives a reference signal transmitted by a second UE. Atblock 2220, the first UE transmits to a network node a report indicatingthat the reference signal was received. At block 2230, the first UEreceives from the network node information indicating that the second UEis in the proximity of the first UE.

The embodiments disclosed herein allow for the configuration ofproximity discovery signals. Pattern-based proximity signaling allowsfor simple detection and reporting by other UEs according to the patternand signal details observed. The mechanism allows for easy tracking ofdetected UEs. Patterns for half-duplex UEs allow all UEs an opportunityto detect all other UEs in a system. Knowledge of patterns by detectingUEs allows for soft combining of multiple transmissions for detection.Limited-time proximity signaling does not require deallocation, as atime-out may occur. Limited-time proximity signaling also minimizessignaling of proximity signals, which may be efficient for one-timeproximity discovery, and simplifies multiplexing of the proximitytransmissions and receptions of many UEs. The embodiments providemaximum proximity detection opportunities for a minimum allocation ofresources otherwise in use by the network.

The above may be implemented by a network element. A simplified networkelement is shown with regard to FIG. 23. In the figure, network element3110 includes a processor 3120 and a communications subsystem 3130,where the processor 3120 and communications subsystem 3130 cooperate toperform the methods described above.

Further, the above may be implemented by a UE. One exemplary device isdescribed below with regard to FIG. 24. UE 3200 is typically a two-waywireless communication device having voice and data communicationcapabilities. UE 3200 generally has the capability to communicate withother computer systems on the Internet. Depending on the exactfunctionality provided, the UE may be referred to as a data messagingdevice, a two-way pager, a wireless e-mail device, a cellular telephonewith data messaging capabilities, a wireless Internet appliance, awireless device, a mobile device, or a data communication device, asexamples.

Where UE 3200 is enabled for two-way communication, it may incorporate acommunication subsystem 3211, including a receiver 3212 and atransmitter 3214, as well as associated components such as one or moreantenna elements 3216 and 3218, local oscillators (LOs) 3213, and aprocessing module such as a digital signal processor (DSP) 3220. As willbe apparent to those skilled in the field of communications, theparticular design of the communication subsystem 3211 will be dependentupon the communication network in which the device is intended tooperate.

Network access requirements will also vary depending upon the type ofnetwork 3219. In some networks network access is associated with asubscriber or user of UE 3200. A UE may require a removable useridentity module (RUIM) or a subscriber identity module (SIM) card inorder to operate on a network. The SIM/RUIM interface 3244 is normallysimilar to a card-slot into which a SIM/RUIM card can be inserted andejected. The SIM/RUIM card can have memory and hold many keyconfigurations 3251, and other information 3253 such as identification,and subscriber related information.

When required network registration or activation procedures have beencompleted, UE 3200 may send and receive communication signals over thenetwork 3219. As illustrated in the figure, network 3219 can consist ofmultiple base stations communicating with the UE.

Signals received by antenna 3216 through communication network 3219 areinput to receiver 3212, which may perform such common receiver functionsas signal amplification, frequency down conversion, filtering, channelselection and the like. Analog to digital (A/D) conversion of a receivedsignal allows more complex communication functions such as demodulationand decoding to be performed in the DSP 3220. In a similar manner,signals to be transmitted are processed, including modulation andencoding for example, by DSP 3220 and input to transmitter 3214 fordigital to analog (D/A) conversion, frequency up conversion, filtering,amplification and transmission over the communication network 3219 viaantenna 3218. DSP 3220 not only processes communication signals, butalso provides for receiver and transmitter control. For example, thegains applied to communication signals in receiver 3212 and transmitter3214 may be adaptively controlled through automatic gain controlalgorithms implemented in DSP 3220.

UE 3200 generally includes a processor 3238 which controls the overalloperation of the device. Communication functions, including data andvoice communications, are performed through communication subsystem3211. Processor 3238 also interacts with further device subsystems suchas the display 3222, flash memory 3224, random access memory (RAM) 3226,auxiliary input/output (I/O) subsystems 3228, serial port 3230, one ormore keyboards or keypads 3232, speaker 3234, microphone 3236, othercommunication subsystem 3240 such as a short-range communicationssubsystem and any other device subsystems generally designated as 3242.Serial port 3230 could include a USB port or other port known to thosein the art.

Some of the subsystems shown in the figure perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as keyboard 3232 and display3222, for example, may be used for both communication-related functions,such as entering a text message for transmission over a communicationnetwork, and device-resident functions such as a calculator or tasklist.

Operating system software used by the processor 3238 may be stored in apersistent store such as flash memory 3224, which may instead be aread-only memory (ROM) or similar storage element (not shown). Thoseskilled in the art will appreciate that the operating system, specificdevice applications, or parts thereof, may be temporarily loaded into avolatile memory such as RAM 3226. Received communication signals mayalso be stored in RAM 3226.

As shown, flash memory 3224 can be segregated into different areas forboth computer programs 3258 and program data storage 3250, 3252, 3254and 3256. These different storage types indicate that each program canallocate a portion of flash memory 3224 for their own data storagerequirements. Processor 3238, in addition to its operating systemfunctions, may enable execution of software applications on the UE. Apredetermined set of applications that control basic operations,including at least data and voice communication applications forexample, will normally be installed on UE 3200 during manufacturing.Other applications could be installed subsequently or dynamically.

Applications and software may be stored on any computer readable storagemedium. The computer readable storage medium may be a tangible or intransitory/non-transitory medium such as optical (e.g., CD, DVD, etc.),magnetic (e.g., tape) or other memory known in the art.

One software application may be a personal information manager (PIM)application having the ability to organize and manage data itemsrelating to the user of the UE such as, but not limited to, e-mail,calendar events, voice mails, appointments, and task items. Naturally,one or more memory stores may be available on the UE to facilitatestorage of PIM data items. Such PIM application may have the ability tosend and receive data items, via the wireless network 3219. Furtherapplications may also be loaded onto the UE 3200 through the network3219, an auxiliary I/O subsystem 3228, serial port 3230, short-rangecommunications subsystem 3240 or any other suitable subsystem 3242, andinstalled by a user in the RAM 3226 or a non-volatile store (not shown)for execution by the processor 3238. Such flexibility in applicationinstallation increases the functionality of the device and may provideenhanced on-device functions, communication-related functions, or both.For example, secure communication applications may enable electroniccommerce functions and other such financial transactions to be performedusing the UE 3200.

In a data communication mode, a received signal such as a text messageor web page download will be processed by the communication subsystem3211 and input to the processor 3238, which may further process thereceived signal for output to the display 3222, or alternatively to anauxiliary I/O device 3228.

A user of UE 3200 may also compose data items such as email messages forexample, using the keyboard 3232, which may be a complete alphanumerickeyboard or telephone-type keypad, among others, in conjunction with thedisplay 3222 and possibly an auxiliary I/O device 3228. Such composeditems may then be transmitted over a communication network through thecommunication subsystem 3211.

For voice communications, overall operation of UE 3200 is similar,except that received signals may typically be output to a speaker 3234and signals for transmission may be generated by a microphone 3236.Alternative voice or audio I/O subsystems, such as a voice messagerecording subsystem, may also be implemented on UE 3200. Although voiceor audio signal output is preferably accomplished primarily through thespeaker 3234, display 3222 may also be used to provide an indication ofthe identity of a calling party, the duration of a voice call, or othervoice call related information for example.

Serial port 3230 may normally be implemented in a personal digitalassistant (PDA)-type UE for which synchronization with a user's desktopcomputer (not shown) may be desirable, but is an optional devicecomponent. Such a port 3230 may enable a user to set preferences throughan external device or software application and may extend thecapabilities of UE 3200 by providing for information or softwaredownloads to UE 3200 other than through a wireless communicationnetwork. The alternate download path may for example be used to load anencryption key onto the device through a direct and thus reliable andtrusted connection to thereby enable secure device communication. Aswill be appreciated by those skilled in the art, serial port 3230 canfurther be used to connect the UE to a computer to act as a modem.

Other communications subsystems 3240, such as a short-rangecommunications subsystem, is a further optional component which mayprovide for communication between UE 3200 and different systems ordevices, which need not necessarily be similar devices. For example, thesubsystem 3240 may include an infrared device and associated circuitsand components or a Bluetooth™ communication module to provide forcommunication with similarly enabled systems and devices. Subsystem 3240may further include non-cellular communications such as WiFi or WiMAX.

The UE and other components described above might include a processingcomponent that is capable of executing instructions related to theactions described above. FIG. 25 illustrates an example of a system 3300that includes a processing component 3310 suitable for implementing oneor more embodiments disclosed herein. In addition to the processor 3310(which may be referred to as a central processor unit or CPU), thesystem 3300 might include network connectivity devices 3320, randomaccess memory (RAM) 3330, read only memory (ROM) 3340, secondary storage3350, and input/output (I/O) devices 3360. These components mightcommunicate with one another via a bus 3370. In some cases, some ofthese components may not be present or may be combined in variouscombinations with one another or with other components not shown. Thesecomponents might be located in a single physical entity or in more thanone physical entity. Any actions described herein as being taken by theprocessor 3310 might be taken by the processor 3310 alone or by theprocessor 3310 in conjunction with one or more components shown or notshown in the drawing, such as a digital signal processor (DSP) 3380.Although the DSP 3380 is shown as a separate component, the DSP 3380might be incorporated into the processor 3310.

The processor 3310 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 3320,RAM 3330, ROM 3340, or secondary storage 3350 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one CPU 3310 is shown, multiple processors may bepresent. Thus, while instructions may be discussed as being executed bya processor, the instructions may be executed simultaneously, serially,or otherwise by one or multiple processors. The processor 3310 may beimplemented as one or more CPU chips.

The network connectivity devices 3320 may take the form of modems, modembanks, Ethernet devices, universal serial bus (USB) interface devices,serial interfaces, token ring devices, fiber distributed data interface(FDDI) devices, wireless local area network (WLAN) devices, radiotransceiver devices such as code division multiple access (CDMA)devices, global system for mobile communications (GSM) radio transceiverdevices, universal mobile telecommunications system (UMTS) radiotransceiver devices, long term evolution (LTE) radio transceiverdevices, worldwide interoperability for microwave access (WiMAX)devices, and/or other well-known devices for connecting to networks.These network connectivity devices 3320 may enable the processor 3310 tocommunicate with the Internet or one or more telecommunications networksor other networks from which the processor 3310 might receiveinformation or to which the processor 3310 might output information. Thenetwork connectivity devices 3320 might also include one or moretransceiver components 3325 capable of transmitting and/or receivingdata wirelessly.

The RAM 3330 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 3310. The ROM 3340 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 3350. ROM 3340 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 3330 and ROM 3340 istypically faster than to secondary storage 3350. The secondary storage3350 is typically comprised of one or more disk drives or tape drivesand might be used for non-volatile storage of data or as an over-flowdata storage device if RAM 3330 is not large enough to hold all workingdata. Secondary storage 3350 may be used to store programs that areloaded into RAM 3330 when such programs are selected for execution.

The I/O devices 3360 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input/output devices. Also, thetransceiver 3325 might be considered to be a component of the I/Odevices 3360 instead of or in addition to being a component of thenetwork connectivity devices 3320.

In an embodiment, a method for communication in a wirelesstelecommunications system is provided. The method comprises receiving,by a UE, configuration information specifying at least one transmissionopportunity in which the UE is to transmit a first reference signal andfurther specifying at least one parameter applicable to the transmissionof the first reference signal. The method further comprisestransmitting, by the UE, the first reference signal in the specifiedtransmission opportunity. The configuration information is received viaat least one of radio resource control signaling or medium accesscontrol signaling, and the transmission opportunity occurs as one of asingle transmission opportunity or a portion of a pattern oftransmission opportunities.

In another embodiment, another method for communication in a wirelesstelecommunications system is provided. The method comprises receiving,by a first UE, a reference signal transmitted by a second UE andtransmitting, by the first UE to a network node, a report indicatingthat the reference signal was received. The reference signal is receivedin a detection opportunity that occurs as one of a single detectionopportunity or a portion of a pattern of detection opportunities.

In another embodiment, a network node is provided. The network nodecomprises a transmission component, a reception component, and aprocessing component. The transmission component is configured such thatthe network node transmits, to a first UE, configuration informationspecifying at least one transmission opportunity in which the first UEis to transmit a reference signal and further specifying at least oneparameter applicable to the transmission of the reference signal. Thereception component is configured such that the network node receives,from a second UE, a report indicating that the second UE received thereference signal from the first UE. The processing component isconfigured such that the network node determines, based on the report,that the first UE is in the proximity of the second UE.

The following is incorporated herein by reference for all purposes: 3GPPTechnical Specification (TS) 36.331.

The embodiments described herein are examples of structures, systems ormethods having elements corresponding to elements of the techniques ofthis application. This written description may enable those skilled inthe art to make and use embodiments having alternative elements thatlikewise correspond to the elements of the techniques of thisapplication. The intended scope of the techniques of this applicationthus includes other structures, systems or methods that do not differfrom the techniques of this application as described herein, and furtherincludes other structures, systems or methods with insubstantialdifferences from the techniques of this application as described herein.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the scopeof the present disclosure. The present examples are to be considered asillustrative and not restrictive, and the intention is not to be limitedto the details given herein. For example, the various elements orcomponents may be combined or integrated in another system or certainfeatures may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A method for communication in a wirelesstelecommunications system, the method comprising: receiving, by a firstuser equipment (UE), a proximity beacon transmitted by a second UEaccording to at least one parameter applicable to the proximity beacon,wherein the proximity beacon is transmitted in a medium access control(MAC) message over a physical layer (PHY) channel; transmitting, by thefirst UE to a network node, a report indicating that the proximitybeacon was received and a transmission opportunity during which theproximity beacon was received; and receiving, by the first UE and fromthe network node, an identity associated with the second UE according tocontents of the proximity beacon and in response to transmitting thereport to the network node, wherein the proximity beacon is received ina detection opportunity that occurs as a portion of a pattern ofdetection opportunities, wherein the at least one parameter comprisesthe pattern and a transmission window defining a period including thetransmission opportunity during which the proximity beacon is received,the pattern indicating a set of subframes in which the proximity beaconis to be transmitted during the transmission window, and wherein thefirst UE soft combines multiple transmissions of the proximity beaconbased on the pattern of the detection opportunities.
 2. The method ofclaim 1, wherein the first UE transmits another proximity beacon thathas a second at least one parameter that is the same as the at least oneparameter of the proximity beacon transmitted by the second UE, whereinthe transmission of the other beacon occurs in the transmissionopportunity at a different time and in a different subframe than thedetection opportunity in which the first UE receives the proximitybeacon from the second UE.
 3. The method of claim 2, wherein thetransmission opportunity and the detection opportunity occur as aportion of a pattern of transmission opportunities and detectionopportunities, and wherein the pattern of transmission opportunities anddetection opportunities is configured such that the first UE has atleast one transmission opportunity to each other UE in a plurality ofUEs that includes the first UE and has at least one detectionopportunity from each other UE.
 4. The method of claim 3, wherein thepattern of transmission opportunities and detection opportunities isconfigured such that a total amount of time for transmissionopportunities and detection opportunities is minimized.
 5. The method ofclaim 2, wherein the report to the network node includes an identifierassociated with at least one of the transmission opportunity and theparameter of the proximity beacon received by the first UE.
 6. Themethod of claim 1, wherein the first UE is provided with an indicationof an action the first UE is to take for detection in cases where beacontransmission or reception is configured to occur when the first UE is ina discontinuous reception (DRX) OFF state, the indication of the actionspecifying that the first UE shall remain in the DRX OFF state for onlytransmission or reception of proximity beacons, but not both.
 7. Themethod of claim 1, wherein the first UE tracks the second UE by at leastone of: not attempting to detect proximity beacons from any UEs otherthan the second UE; or attempting to detect proximity beacons from thesecond UE more frequently than attempting to detect proximity beaconsfrom UEs other than the second UE.
 8. The method of claim 1, wherein thefirst UE attempts to detect at least one of: all proximity beaconsavailable to the first UE; or a subset of all proximity beaconsavailable to the first UE, wherein the subset is specified by thenetwork node.
 9. The method of claim 1, wherein at least one proximitybeacon for the first UE to detect is indicated by specifying resources,in at least one of: a system information block (SIB) message or a radioresource control message (RRC), where the proximity beacons aretransmitted, and wherein the first UE attempts to detect all proximitybeacons in the resources.
 10. The method of claim 1, wherein the reportprovides at least one of: an indication that the proximity beacontransmitted by the second UE was detected; or an indication of thestrength of the proximity beacon transmitted by the second UE.
 11. Anon-transitory computer medium storing computer readable instructionsexecutable by a processor to implement a method for communication in awireless telecommunications system, the method comprising: receiving, bya first user equipment (UE), a proximity beacon transmitted by a secondUE according to at least one parameter applicable to the proximitybeacon, wherein the proximity beacon is transmitted in a medium accesscontrol (MAC) message over a physical layer (PHY) channel; transmitting,by the first UE to a network node, a report indicating that theproximity beacon was received and a transmission opportunity duringwhich the proximity beacon was received; and receiving, by the first UEand from the network node, an identity associated with the second UEaccording to contents of the proximity beacon and in response totransmitting the report to the network node, wherein the proximitybeacon is received in a detection opportunity that occurs as a portionof a pattern of detection opportunities, wherein the at least oneparameter comprises the pattern and a transmission window defining aperiod including the transmission opportunity during which the proximitybeacon is received, the pattern indicating a set of subframes in whichthe proximity beacon is to be transmitted during the transmissionwindow, and wherein the first UE soft combines multiple transmissions ofthe proximity beacon based on the pattern of the detectionopportunities.
 12. The non-transitory computer medium of claim 11,wherein the first UE transmits another proximity beacon that has asecond at least one parameter that is the same as the at least oneparameter of the proximity beacon transmitted by the second UE, whereinthe transmission of the other beacon occurs in the transmissionopportunity at a different time and in a different subframe than thedetection opportunity in which the first UE receives the proximitybeacon from the second UE.
 13. The non-transitory computer medium ofclaim 12, wherein the transmission opportunity and the detectionopportunity occur as a portion of a pattern of transmissionopportunities and detection opportunities, and wherein the pattern oftransmission opportunities and detection opportunities is configuredsuch that the first UE has at least one transmission opportunity to eachother UE in a plurality of UEs that includes the first UE and has atleast one detection opportunity from each other UE.
 14. Thenon-transitory computer medium of claim 13, wherein the pattern oftransmission opportunities and detection opportunities is configuredsuch that a total amount of time for transmission opportunities anddetection opportunities is minimized.
 15. The non-transitory computermedium of claim 12, wherein the report to the network node includes anidentifier associated with at least one of the transmission opportunityand the parameter of the proximity beacon received by the first UE. 16.The non-transitory computer medium of claim 11, wherein the first UE isprovided with an indication of an action the first UE is to take fordetection in cases where beacon transmission or reception is configuredto occur when the first UE is in a discontinuous reception (DRX) OFFstate, the indication of the action specifying that the first UE shallremain in the DRX OFF state for only transmission or reception ofproximity beacons, but not both.
 17. The non-transitory computer mediumof claim 11, wherein the first UE tracks the second UE by at least oneof: not attempting to detect proximity beacons from any UEs other thanthe second UE; or attempting to detect proximity beacons from the secondUE more frequently than attempting to detect proximity beacons from UEsother than the second UE.
 18. The non-transitory computer medium ofclaim 11, wherein the first UE attempts to detect at least one of: allproximity beacons available to the first UE; or a subset of allproximity beacons available to the first UE, wherein the subset isspecified by the network node.
 19. The non-transitory computer medium ofclaim 11, wherein at least one proximity beacon for the first UE todetect is indicated by specifying resources, in at least one of: asystem information block (SIB) message or a radio resource controlmessage (RRC), where the proximity beacons are transmitted, and whereinthe first UE attempts to detect all proximity beacons in the resources.20. The non-transitory computer medium of claim 11, wherein the reportprovides at least one of: an indication that the proximity beacontransmitted by the second UE was detected; or an indication of thestrength of the proximity beacon transmitted by the second UE.
 21. Auser equipment (UE), the UE comprising: a storage device; and aprocessor configured to execute instructions stored on the storagedevice such that when executed, cause the UE to: receive a proximitybeacon transmitted by a second UE according to at least one parameterapplicable to the proximity beacon, wherein the proximity beacon istransmitted in a medium access control (MAC) message over a physicallayer (PHY) channel; transmit, to a network node, a report indicatingthat the proximity beacon was received and a transmission opportunityduring which the proximity beacon was received; and receive, from thenetwork node, an identity associated with the second UE according tocontents of the proximity beacon and in response to transmitting thereport to the network node, wherein the proximity beacon is received ina detection opportunity that occurs as a portion of a pattern ofdetection opportunities, wherein the at least one parameter comprisesthe pattern and a transmission window defining a period including thetransmission opportunity during which the proximity beacon is received,the pattern indicating a set of subframes in which the proximity beaconis to be transmitted during the transmission window, and wherein the UEsoft combines multiple transmissions of the proximity beacon based onthe pattern of the detection opportunities.
 22. The UE of claim 21,wherein the UE transmits another proximity beacon that has a second atleast one parameter that is the same as the at least one parameter ofthe proximity beacon transmitted by the second UE, wherein thetransmission of the other beacon occurs in the transmission opportunityat a different time and in a different subframe than the detectionopportunity in which the UE receives the proximity beacon from thesecond UE.
 23. The UE of claim 22, wherein the transmission opportunityand the detection opportunity occur as a portion of a pattern oftransmission opportunities and detection opportunities, and wherein thepattern of transmission opportunities and detection opportunities isconfigured such that the UE has at least one transmission opportunity toeach other UE in a plurality of UEs that includes the UE and has atleast one detection opportunity from each other UE.
 24. The UE of claim23, wherein the pattern of transmission opportunities and detectionopportunities is configured such that a total amount of time fortransmission opportunities and detection opportunities is minimized. 25.The UE of claim 22, wherein the report to the network node includes anidentifier associated with at least one of the transmission opportunityand the parameter of the proximity beacon received by the UE.
 26. The UEof claim 21, wherein the UE is provided with an indication of an actionthe UE is to take for detection in cases where beacon transmission orreception is configured to occur when the UE is in a discontinuousreception (DRX) OFF state, the indication of the action specifying thatthe UE shall remain in the DRX OFF state for only transmission orreception of proximity beacons, but not both.
 27. The UE of claim 21,wherein the UE tracks the second UE by at least one of: not attemptingto detect proximity beacons from any UEs other than the second UE; orattempting to detect proximity beacons from the second UE morefrequently than attempting to detect proximity beacons from UEs otherthan the second UE.
 28. The UE of claim 21, wherein the UE attempts todetect at least one of: all proximity beacons available to the UE; or asubset of all proximity beacons available to the UE, wherein the subsetis specified by the network node.
 29. The UE of claim 21, wherein atleast one proximity beacon for the UE to detect is indicated byspecifying resources, in at least one of: a system information block(SIB) message or a radio resource control message (RRC), where theproximity beacons are transmitted, and wherein the UE attempts to detectall proximity beacons in the resources.
 30. The UE of claim 21, whereinthe report provides at least one of: an indication that the proximitybeacon transmitted by the second UE was detected; or an indication ofthe strength of the proximity beacon transmitted by the second UE.